(define (fee age)
	(cond
		((or (<= age 3) (>= age 65)) 0)
		((<= 4  age 6) 0.5)
		((<= 7  age 12) 1.0)
		((<= 13 age 15) 1.5)
		((<= 16 age 18) 1.8)
		(else 2.0)))
